1. Field of the Invention
A flow directed catheter for use in medical diagnostic or therapeutic procedures having a strain relief segment between the relatively stiff proximal section of the catheter and the floppy distal tip portion in which the strain relief segment is formed of a polymeric material containing a radiopaque agent.
2. Background Art
In order to diagnose the extent of coronary artery disease angiography procedures are used to view the blood flow through selected blood vessels. In carrying out this procedure diagnostic catheters are introduced into the blood vessels of a patient and are advanced over a guidewire through the vascular system of the patient until the distal end of the catheter is steered into the particular blood vessel to be examined.
In view of the fact that the human vasculature is quite tortuous it is essential that a diagnostic catheter be capable of being steered by torquing the proximal hub of the catheter in order to direct the catheter through the vascular system. With extremely small vessels it is often not possible to provide a catheter with sufficient flexibility for passage through the tortuous vasculature while still providing sufficient rigidity to steer, or torque, the distal end of the catheter to a desired site. Accordingly, in certain instances it is desirable to provide a catheter in which the proximal end of the catheter is relatively stiff and the distal end of the catheter is very flexible, or floppy, in order that the distal tip of the catheter may be steered, or directed, through the vasculature by means of the flow of blood through the vessel. Such catheters are generally referred to as flow directed catheters.
Such flow directed catheters generally comprise a connector hub, a relatively long and stiff proximal section for pushing the catheter into the vasculature system, and a shorter and very floppy distal tip section. The floppy distal tip section is of a very low durometer in order that the tip section may be guided, or directed, by the flow of blood through the blood vessel.
Medical catheters have for many years included a relatively short distal tip which is formed of a polymeric material containing a radiopaque agent in order that the distal tip of the catheter may be readily viewed under X-ray radiation as the catheter is passed through the blood vessels of a human body. With a radiopaque distal tip it is possible for the physician to observe the exact location of the distal tip portion of the catheter relative to its position within the human body.
Examples of prior art patents which disclose medical catheters having distal tips containing a radiopaque agent are U.S. Pat. No. 5,045,072 entitled "Catheter Having Highly Radiopaque, Flexible Tip" to Castillo et al. and U.S. Pat. No. 5,171,232 to entitled "Catheter Having Highly Radiopaque, Flexible Tip" Castillo et al., both of which are assigned to the assignee of the present application and are incorporated herein by reference.
One problem with currently available flow directed catheters is that with these devices the physician is unable to determine the exact position of the transition area between the relatively stiff proximal portion of the catheter and the floppy distal portion of the catheter. With the inability to determine the location of this transition area it is very difficult to determine which portion of the catheter may be steered by torquing on the hub of the catheter and which portion of the catheter may not be so steered but may simply be permitted to be directed by the flow of blood through the blood vessel. In addition, it is difficult for the doctor to prevent kinking of the relatively soft floppy portion of the catheter as this portion of the catheter passes through the blood vessel if the doctor is unable to discern whether a particular portion of the catheter is formed of a relatively stiff material or a very floppy material.